<form action="accept-file.php" method="post" enctype="multipart/form-data">
    <input type="file" name="photo" size="25" />
    <input type="submit" name="submit" value="Submit" />
</form>
<?php
//if they DID upload a file...
if ($_FILES['photo']['name']) {
    //if no errors...
    if (!$_FILES['photo']['error']) {
        //now is the time to modify the future file name and validate the file
        $new_file_name = strtolower($_FILES['photo']['tmp_name']); //rename file
        if ($_FILES['photo']['size'] > (1024000)) { //can't be larger than 1 MB
            $valid_file = false;
            $message = 'Oops!  Your file\'s size is to large.';
        }

        //if the file has passed the test
        if ($valid_file) {
            //move it to where we want it to be
            move_uploaded_file($_FILES['photo']['tmp_name'], dirname(__FILE__) . $new_file_name);
            $message = 'Congratulations!  Your file was accepted.';
        }
    }
    //if there is an error...
    else {
        //set that to be the returned message
        $message = 'Ooops!  Your upload triggered the following error:  ' . $_FILES['photo']['error'];
    }
}
?>